Vocal communication is essential for courtship among many vertebrates. Studies in teleost fish provide considerable evidence that vocalizations are controlled by distinct neural circuits which show seasonal and sex differences in response to circulating levels of steroid hormones. Prior in vivo work has also shown that steroids can induce rapid changes in 'fictive vocalization.' This application will focus on the teleost vocal pattern generator located in the hindbrain-spinal region since it provides the simplest vertebrate preparation for determining how steroid hormones modulate the properties of pacemaker and motor neurons that lead to vocalization within a social context. An electrophysiological approach will be used to describe steroid-induced changes in vocal patterning at the level of intrinsic membrane properties of these identified neurons with the development of an in vitro preparation. The central goal of this research is to understand how steroid hormones modulate the production of highly stereotyped sounds for vocal communication by mediating changes in neuronal membrane properties via both rapid, non-genomic mechanisms and longer acting mechanisms mediated by nuclear hormone receptors.